Answer:
Step-by-step explanation:
Given that a referral code is 2 letters (A-Z, no lowercases) followed by 4 digits (0-9), or it is 2 digits (0-9) followed by four letters (A-Z, no lowercases).
Digits are not allowed to repeat but letters can repeat.
Thus we find that 2 letters can be selected in
[tex]26^2 ways[/tex]
Since for numbers repitition is not allowed, 4 digits can be arranged in 9P4 ways
= 9*8*7*6
Total no of ways for I type=[tex]26^2*9*8*7*6[/tex]
For II type numbers are 2 and letters are 4.
So no of ways = [tex]9P2 *26^4[/tex]
total referral codes possible =
[tex]26^2*9*8*7*6+26^4 *9*8\\= 26^2 (9)(8) [42+676]\\= 34946496[/tex]
